suggestions for debugging code

[Matthew Knepley]

On Tue, Jul 28, 2009 at 10:17 AM, Randall Mackie <rlmackie862 at gmail.com>wrote:

> I have run into a very difficult debugging problem. I have recently made
> some
> modifications to my PETSc code, to add some new features. When I compiled
> the
> code in debug mode (we are using the Intel compilers and mvapich on
> Infiniband),
> the code runs fine with any number of processes.
>
> When the code is compiled in optimize mode, it runs fine on, say, up to 32
> processes,
> but not 64, bombing out someplace strange, with a Segmentation Violation.
>
> I've tried using Valgrind, but you can't use it with PETSc and my code
> compiled in
> Debug mode because the code finishes successfully, and the other problem I
> have with


Sometimes valgrind will catch things even when code does not crash.


>
> Valgrind + mvapich is there are about a million messages spewed out, making
> it
> extremely difficult to see if there are really any issues in MY code. I've
> thought
> to have PETSc download and compile MPICH2, which I would hope would produce
> less
> output from Valgrind.


In order to filter these out, you use a "suppressions file" for valgrind.
The manual has a
good section on this and it should not be hard to wipre out most of them.
Satish designed
one for our unit tests.

  Matt


>
> Anyone have any suggestions on how to debug this tricky situation? Any
> suggestions
> would be greatly appreciated.
>
> Randy
>



-- 
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
lead.
-- Norbert Wiener
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